Alloy



Patented June 23, 1936 UNITED STATES PATENT OFFICE v ALLOY Roy E. Paine, Oakland, Calif., assignor, by mesne assignments, to Magnesium Development Corporation, a corporation of Delaware No Drawing. Original application October 4,

1933, Serial No. 692,135. Divided and this application November 15, 1935, Serial No. 49,969

. p 2 Claims. (01. 75-168) The invention relates to magnesium-base alpreferred casting alloys are those containing loys and is directed to the development of alloys above-about 5 per cent of lead since it is in these of this class which have good corrosion resistalloys that the most pronounced combination of ance, particularly in the cast and in the cast and these diflerent properties is obtained. The alloy 5 heat treated condition. may be worked byextrusion over a range of from The art of casting magnesium presents many about 0.5 per cent to about 22.0 per cent of lead. practical difficulties which must be surmounted As an all around casting alloy, I have found a before the true commercial possibilities of magmagnesium alloy containing 5 to per cent of nesium castings can be fully realized. An alloy lead to be particularly adapted to general found- 10 which is suitable for one application may be enry purposes. Alloys falling within this pretirely unsuited to another and, as a consequence, ferred rangeof composition as well as other alit is frequently necessary to sacrifice desirable loys comprised within the broader limits precharacteristics of the alloy in order to more fully Viously defined, have been Subjected o Severe realize the advantages of some one or more imtests designed to produce accelerated corrosion. l5 portant characteristics. Thus a compromise Sand cast test bars poured in accordance with must quite frequently be made in order to apthe best casting practice in the art were subproach in one alloy the optimum properties for jected to corrosion tests in the as cast and in a given application. For example, it may be the heat treated condition. In the example refound that corrosion resistance can be sacrificed ferred to the'heat treatment was carried out at to a certain extent to obtain higher tensile about 459 centigrade for about 20 hours folstrength, yield point, hardness, or similar melowed by quenching in water, and both heat chanical properties. Again, tensile strength may treated and unheat treated test bars were subbe sacrificed in order to obtain proper casting or jected to that corrosion test which comprises alworking characteristics. It is an object of the 'tern'ately immersing the metal in, and removpresent invention to develop magnesium alloys ing it from, a. 3 per cent sodium chloride soluwhich will combine to a maximum degree the tion'for about 80 hours, a treatment referred to. characteristics of corrosion resistance, favorable hereinafter as the alternate immersion treatmechanical properties, workability, susceptibility ment. to improvement by heat treatment and adapt- There are certain elements which may be addability to sand casting. ed to the binary magnesium-lead alloys to par- A further object is the provision of magnesium ticular advantage. Such, for instance, are the alloys characterized by their susceptibility to be metals calcium, cadmium and zinc. These improved. in mechanical properties by suitable may be added singly or in combination with each thermal treatments. Afurther object isthe proother, the zinc in amounts between about 1.0 vision of magnesium-base alloys characterized by per cent and 10.0-per cent, the calcium between good corrosion resistance in either the cast or in about 0.1 per cent and 2.0 per cent, and the cadthe cast and'heat treated condition. A further mium between about 1.0 per cent and 10.0 per object is the provision of magnesium alloys poscent. These alloying elements are substantial sessing excellent casting characteristics. A furequivalents as indicated by their susceptibility to 40 ther object is the provision of magnesium-base thermal treatment in magnesium-lead alloys.

alloys susceptible, within certain ranges, to me- The calcium favorably affects the casting propchanical deformation. erties of the alloy without markedly decreasing I have discovered that magnesium-base alloys its corrosion resistance. For instance, a magcontaining from 0.5 per cent to 22 per cent of nesium alloy containing 21.4 per cent of lead lead possess to an appreciable degree the 001- and 0.25 percent of calcium shows, in the as lective characteristics of alloys which are resistcast condition, a strength loss of only 17 per cent ant to corrosion, alloys which may be readily after alternate immersion in a 3 per cent socast, alloys which are susceptible to alteration dium chloride solution for about 80 hours-while of properties by thermal treatments, alloys hava heat treated magnesium alloy containing about ing favorable mechanical properties, and alloys 5 per cent of lead to which about 0.25 per cent which, within a restricted range, may be worked of calcium had been added did not undergo any by extrusion, forging, or other means of meappreciable loss in strength under the foregoing chanical deformation. I corrosion conditions; the heat treatment in this In accordance with my invention lead may be case was a treatment at about 450 centigrade present in amounts as low as 0.5 per cent. The for about 20 hours. An alloy of magnesium with a magnesium-base alloy containing about 5.3

per cent of lead and about 5.0 per cent of cadmium. An alloy of magnesium with about 5.0 per cent of lead and 5.0 per cent of zinc had'in the sand cast condition a tensile strength of about 23,370 pounds per square inch. After a thermal treatment of about hours at 450 centigrade followed by an aging treatment of mium, balance magnesium; (3) 5.0 per cent lead,

5.0 per cent zinc, balance magnesium. If more silicon does not exceed 15.0 per cent. 55

about 20 hours at 150 centigrade its strength had increased to about 25,710 pounds per square inch. After an alternate immersion corrosion test of hours the loss in strength was on'ly;12 per' cent. Another alloy of magnesium with about 5.2 per cent of lead and 3.2 per cent of zinc under similar conditions lost only about 10 per cent after 80 hours alternate immersion in the corrosive solution. As a preferred composition for alloys of this nature I advise 1) 5.0 per cent lead, 1.0 percent calcium, balance magnesium; (2) 5.0 per cent lead, 5.0 per cent cadthan one of the elements calcium, cadmium. or zinc be present simultaneously, I prefer not to exceed a total of 10.0 per cent for these elements.

One of the disadvantages of the alloys described herein which may aifect their use in certain applications, particularly where high strength is a leading or very material consideration, is the fact that the grain structure of these alloys (with or without calcium) tends to be coarse. I have found that the metals aluminum and silicon form a class of alloying elements which may be added to magnesium-lead alloys and are substantially equivalent in this respect that they materially refine the grain structure of the alloy. Aluminum, for instance, can be added over a wide range, such as between 1.0 and 15.0 per cent; silicon may be effectively present for this purpose in amounts ofabout 0.1 to 2.0 per cent. When used in combination it is advisable that the total content of aluminum and preferred practice of my invention I have found that the best results are usually obtained when the aluminum is present in amounts between 5 and 10 per cent. l

As a preferred magnesium-lead-silicon composition 1 use a magnesium-base alloy containing 7.0 per cent of lead and 0.5 percent of silicon. As a preferred magnesium-lead-aluminum alloy I use a magnesium-base alloy containing 7.0 per cent of lead and 5.0 per cent of aluminum. When the aluminum and silicon are used in conjunction I prefer to use a total of about 5.0 per cent of aluminum and silicon combined, for instance about 4.0 per cent aluminum and 1.0 per cent silicon.

Manganese alone may be added to magnesiumlead alloys in amounts between 0.1 per cent and 1.0- per cent and has a stabilizing effect upon the alloy properties in that it raises the hardness slightly, does not materially decrease the corrosion resistance. and adds to the matrix of the In thealloy a hardening element which expresses itself not only in .an increase in tensfle strength but also in surface hardness. An alloy of this nature containing about 8.0 per cent of lead and 0.85 per cent of manganese lost only 6 per cent of its original strength ,after 80 hours alternate immersionin a 3 per cent aqueous solution of sodium chloride and in the solution heat treated condition lost only 7 per cent of its strength in the alternate immersion treatment. A magnesium alloy containing about 10.37 per cent of lead had lost only about 10 per cent of its strength at the .expiration of this period as compared with certain other commercialalloys,

such as, for instance, the well known magnesium alloy containing about 7 per cent of aluminum 'and- 0.4 per cent of manganese which, at the end of 40 hours of alternateimmersion, had lost about. 60v per cent of its strength.v

. Very favorable alloys can be compounded by using as a base an alloy of magnesium, lead and aluminum and making additions thereto of at least one of the class of metals tin, manganese or zinc. The lead can be used in amounts from about 0.5 per cent to about 22.0 per cent, the

aluminum from about 1.0 per cent to about 15.0

per cent, the tin from about 1.0 per cent to about 15.0 per cent, the manganese from about 0.1 per cent toabout 1.0 per cent, and the zinc from about 1.0 per cent'to about 10.0 per cent. A sand cast alloy within this range had, in the as cast condition, a tensile strength of 27,500 pounds per square inch and an elongation of 5.7 per centin 2 inches. After a thermal treatment of 16 hours at 315 centigrade, the alloy had a tensile strength of 29,640 poun'ds per square inch and an elongation of 6.0 per cent in 2 inches. Some of the heat treated specimens were then given an alternate immersion treatment for 40 hours and after the treatment the specimens had a tensile strength of 28,413 pounds per square inch and an elongation of 5.8 per cent in 2 inches, this alloy containing 5.0 per cent of aluminum, 5.0 per cent o'f'lead, 0.4 per cent of manganese and 2.0 per cent of zinc. The loss in strength on the corrosion treatment is observed to be less than 5 per cent as compared to about 60 per cent with the commercial magnesium-aluminum-manganese alloy disclosed hereinbefore which contains about 7 per cent of aluminum and 0.4 per cent of manganese. As preferred compositions for alloys of this nature I advise (1) 7.0 per cent of lead, 7.0 per cent of aluminum, 2.0 per cent tin, balance magnesium; (2) 7.0 per cent lead, 7.0 per cent aluminum, 2.0 per cent tin, 0.5 per cent manganese, balance magnesium; (3) 7.0 per cent lead, 7.0 per cent aluminum, 2.0 per cent tin, 2.0 per cent zinc, balance magnesium.

Two alloy compositions within this range which I have used to advantage are as follows: A' magnesium-base alloy containing 8.0 per cent of aluminum, 3.0 per cent of lead 0.4 per cent of manganese, 1.0 per cent of zinc, and 3.0 per cent of tin; a magnesium-base alloy containing 8.0 per cent of aluminum, 1.0 per cent of lead, 0.4 per cent of manganese, 1.0 per cent of zinc, and 1.0 per cent of tin.

The addition of lead to the magnesium-alumi num-manganese alloys increases very considerably the corrosion resistance of these alloys, since with the addition of about 7 per cent of lead to an alloy containing 7 per cent of aluminum and 1 per cent of manganese, the loss of strensthafterthealtemateimmenlontcstwasw only about 30 per cent, as compared with about 60 per cent of the same alloy without lead.

Alloys of magnesium with lead, aluminum, and

manganese have been disclosed hereinabove. 1

37,010 pounds per square inch and its Brinell hardness about 84. As a desirable alloy of this nature I advise 7.0 per cent lead, 7.0 percent aluminum and 0.4 per cent manganese. If more have discovered that if to a base alloy of mag-\ than one of the elements calcium or cadmium nesium-lead-aluminum-manganese I add one or more of the class of metals calcium or cadmium,

the resulting alloys become considerably more susceptible to variation of properties by thermal treatments and their hardness can be markedly increased by artificial aging after thermal solution treatments. In these alloys the lead content should range from about 0.5 per cent to about 22.0 per cent, the aluminum from about 1.0 per cent to about 15.0 per cent, and the manganese from about 0.1 per. cent to about 1.0 per cent.

To these elements as a common base I add the elements calcium, or cadmium, singly or in combination, the calcium in amounts from about 0.1 per cent to about 2.0 per cent, the cadmium from about 1.0 per cent to about 10.0 per cent. As an example of an alloy of this nature, a sand cast specimen of a magnesium-base alloy containing about 10.0 per cent of lead, about 7.0 per cent of aluminum, about 0.4 per cent of manganese, and about 5.0 per cent of cadmium, had in the cast condition a tensile strength of about 23,200 pounds per square inch. After a thermal solution treatment of 21 hours at about 430 centigrade the tensile strength of the alloy had increased to about 36,000 pounds per square inch, a gain in strength of about 55 per cent. The

same alloy after the solution treatment had a tensile strength of about 24,000 pounds per square inch. After a thermal treatment of 21 hours at about 430 centigrade the alloy had a tensile strength of about 35,000 pounds per square inch. An additional aging treatment raised. the Brinell hardness of the alloy from about 61 to about 79.

Similarly, a magnesium-base alloy containing about 5.0 per cent of lead, 10.0 per cent of cadmium, 7.0 per cent of aluminum, 1.0 per cent of manganese, and 0.25 per cent ofv calcium had in the sand cast condition a tensile strength of about 24,290 pounds per square inch. After a thermal treatment oi. 20 hours at about 430 centigrade this alloy had a tensile strength of. about 33,200 pounds per square inch. After an additional thermal treatment of about 20 hours at about centigrade the strength increased to about 35,600 pounds per square inch and the Brinell hardness from'a'bout 47 to about 66.

Another magnesium-base alloy containing 7 about 10.0 per cent of lead, 7.0 per cent of aluminum, 5.0 per cent of cadmium, 0.4 per cent ofmanganese, and 0.1 per cent'of calcium, had in the sand cast conditions tensile strengthfof about 23,210 pounds per square inch. After a' thermal solution treatment of 21 hoursat about 430 oentigrade the alloy had a tensile strength of about 36,030 pounds per square inch; the

Brinell hardness was about 61.- After an additional aging treatment of about 20 hours. at about centigrade its tensile strength was about are present simultaneously, the total should not exceed about 10.0 per cent for preferred purposes.

The addition of zinc in amounts from about 1.0 per cent to about 10.0 per cent to magnesiumlead alloys containing aluminum and silicon in combination decreases the linear shrinkage, thus favorably aifecting the casting properties, and also increases the corrosion resistance and raises the yield point of these alloys. In alloys of this type the lead should range from 0.5 per cent to 22.0 per cent, the aluminum from 1.0 per cent to 15.0 per cent, and the silicon from 0.1 per cent to 2.0 per cent, but the total amount of aluminum and silicon should preferably not exceed 15.0 per cent. a

A useful alloy of this nature is a magnesiumbase alloy containing about 10.0 per cent lead, 8.0 per cent aluminum and 3.25 per cent zinc. Another useful composition is attained by substituting about 1.0 per cent silicon for part or all of the aluminum.

An alloy similarly improved in casting properties, although not to such a decided extent, is one containing from about 0.5 per cent to 22.0 per cent of lead, from about 1.0 per cent to about 10.0 per cent of zinc, and from about 0.1 per cent to about 2.0 per cent of silicon. A favorable alloy within this range is a magnesium-base alloy consisting of about 10.0 per cent of lead, about 3.25 per cent of zinc, and about 1.0 per cent of silicon, the balance being substantially magnesium.

In making up alloys of the compositions dis- ,closed hereinabove the alloys may be compounded by any of the methods known in the art. In casting the alloys recourse may be had to the protective measures disclosed in existing patents and the published literature relating to easily oxidizable metals. The alloys, especially the magnesium-lead binary alloys, may be extruded over the entire disclosed composition range, but other types or mechanical deformation such as rolling or forging should be carried on with due regard for the fact that as the percentage of total added alloying elements increases, the necessity for precaution in working the alloy also increases.

It is my object to retain, as far as possible, the advantages of the use of magnesium base, such as low specific gravity, while securing in addition the hereinabove disclosed benefits accruing from the additions oi. the other alloying elements herein outlined. Accordingly, wherein the appended claims the term magnesium-base alloy is used, it refers to an alloy containing more than approximately 50 per cent of magnesium.

This application is a division of my copending application Serial No. 692,135, filed October 4, 1933.

I claim:

1. A magnesium-base alloy containing from about-0.5 to 22.0 per cent of lead, from about 1.0 to 15.0 per cent 01' 'aluminum,from about'0.1 to 1.0 per cent of manganese, and from about 1.0 to 15.0 per cent of tin, the balance being magnesium.

2. A magnesium-base alloy containing about 7.0 per cent of lead, about 7.0 per cent of aluminum, about 0.5 per cent or manganese, and about 2.0 per cent of tin, the balance beingmagnesium.

ROY E. PAINE. 

